Terming the "epidemic" a "real worry" for society, the researchers explained that as a woman ages, the ability of her uterus to contract worsens, meaning she may need help giving birth.

Head researcher Professor Gordon Smith remarked: "As more women delay childbirth, it is essential that we fully understand the effects of age on childbirth if we are to impact on rising rates of intervention in pregnancy."

The fertility rate for women aged between 30 and 34 overtook that of those aged 25 to 29 in 2004 for the first time, according to the Office for National Statistics.